Rotatable and removable multi-pin explosion proof connector assembly

ABSTRACT

A process measurement instrument comprises a process adaptor for mounting to a process vessel or the like and operatively associated with a sensing element for sensing a process variable and including plural electrical conductors. An instrument housing includes a control circuit. A connector assembly is operatively disposed between the instrument housing and the process adaptor for removably connecting the instrument housing to the process adaptor. The connector assembly comprises a first connector including a cylindrical connector body having an offset boss with a first multi-pin wire connector. A second connector includes a cylindrical connector housing, receiving the cylindrical connector body, having an offset bore, receiving the offset boss, and having a second multi-pin wire connector, mateable with the first wire connector, for selectively electrically connecting the control circuit to the sensing element with the offset boss and offset bore ensuring proper alignment of the first and second multi-pin wire connectors.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

MICROFICHE/COPYWRITE REFERENCE

Not Applicable.

FIELD OF THE INVENTION

This invention relates to process control instruments, and moreparticularly, to a removable and rotatable, multi-pin explosion proofconnector.

BACKGROUND

Process control systems require the accurate measurement of processvariables. Typically, a primary element senses the value of a processvariable and a transmitter develops an output having a value that variesas a function of the process variable. For example, a level transmitterincludes a primary element for sensing level and a circuit fordeveloping an electrical signal proportional to or representing sensedlevel.

Knowledge of level in industrial process tanks or vessels has long beenrequired for safe and cost-effective operation of plants. Manytechnologies exist for making level measurements. These includemagnetostrictive, capacitance, ultrasonic and microwave radar, to name afew.

One form of process instrument is of the intrusive type in which theprimary element is in direct contact with the process fluid for sensinglevel. A magnetostrictive transmitter is an example of an intrusive typelevel measurement instrument. A magnetostrictive transmitter has a probeincluding a magnetostrictive wire maintained under tension in a tube.The probe extends into the process vessel. A magnetic float is movableproximate the probe and floats atop the fluid in the vessel. Anelectrical pulse is transmitted on the magnetostrictive wire. Theelectrical pulse interacts with the magnetic field of the float, whichcreates a torque on the wire to produce a torsional force on the wire,thus initiating a torsional wave that propagates along the wire at thespeed of sound. This is known as the Wiedemann effect. Typically, apickup sensor is positioned at one end of the wire to sense thetorsional wave on the wire. The elapsed time is measured between thelaunch of the electrical pulse and the signal from the pickup sensor.The distance between the magnet and the pickup sensor is calculated fromthe measured elapsed time multiplied by the speed of the torsional wave,representing level.

It is often desirable to rotate the transmitter or other electronicshead for ease of viewing of the display or accessing wire compartmentsor the like. Also, it is advantageous to have the transmitter removablefor ease of installation and maintenance. In hazardous environments itis necessary that connection between the transmitter and probe satisfyrequirements for explosion-proof applications.

This application is directed to improvements which allow a transmitterto be rotatable, removable and/or remote mountable.

SUMMARY

In accordance with one aspect there is disclosed a process measurementinstrument comprising a process adaptor for mounting to a process vesselor the like and operatively associated with a sensing element forsensing a process variable and including plural electrical conductors.An instrument housing includes a control circuit. A connector assemblyis operatively disposed between the instrument housing and the processadaptor for removably connecting the instrument housing to the processadaptor. The connector assembly comprises a first connector including acylindrical connector body having an offset boss with a first multi-pinwire connector. A second connector includes a cylindrical connectorhousing, receiving the cylindrical connector body, having an offsetbore, receiving the offset boss, and having a second multi-pin wireconnector, mateable with the first wire connector, for selectivelyelectrically connecting the control circuit to the sensing element withthe offset boss and offset bore ensuring proper alignment of the firstand second multi-pin wire connectors.

It is a feature that the cylindrical connector body comprises a onepiece metal body threaded at one end, opposite the offset boss, forconnection to the process adaptor or the instrument housing.

It is another feature that the cylindrical connector housing comprises aone piece metal housing. The connector housing may include a neck at oneend and a cylindrical swivel secured for rotation around the neck. Theswivel includes an outer thread for connection to the process adaptor orthe instrument housing and enabling rotation of the control housingrelative to the process adaptor. The swivel may include a pin receivablein an arcuate slot in the cylindrical connector housing to limitrotation of the cylindrical swivel. The swivel may include a set screwengaging the neck to selectively prevent rotation of the cylindricalswivel.

It is another feature that the second connector is adapted to provide acylindrical flame path between the cylindrical swivel and the neck andthe cylindrical connector body and the cylindrical connector housing areadapted to provide a second cylindrical flame path to provide anexplosion-proof connector assembly.

It is another feature that the neck comprises a through opening filledwith a potting compound and the cylindrical connector body includes athrough opening filled with a potting compound.

It is yet another feature to provide an elongate cable including a thirdconnector, similar to the first connector, at one end, and a fourthconnector, similar to the second connector, at an opposite end. A cableis connected between the first and second connector to remotely mountthe control housing relative to the process adaptor.

It is an additional feature to provide an O-ring disposed between thecylindrical connector body and a cylindrical connector housing.

It is yet another feature to provide a lock screw receivable in anopening in the cylindrical connector housing engaging the offset boss tosecure the second connector to the first connector.

There is disclosed in accordance with another embodiment a processmeasurement instrument comprising a process adaptor for mounting to aprocess vessel or the like and operatively associated with a sensingelement for sensing a process variable and including plural electricalconductors. An instrument housing includes a control circuit. Aconnector assembly is operatively disposed between the instrumenthousing and the process adaptor for removably connecting the instrumenthousing to the process adaptor. The connector assembly comprises a firstconnector including a cylindrical connector body with a coaxial throughopening and having an offset boss at one end with a first multi-pin wireconnector in the through opening at the offset boss and a firstelectrical cable in the through opening connected to the first multi-pinwire connector. A second connector includes a cylindrical connectorhousing with a coaxial through opening and a first blind bore at oneend, receiving the cylindrical connector body, and an offset blind borein the first blind bore, receiving the offset boss. A second multi-pinwire connector is in the offset blind bore and extends into the throughopening. A second electrical cable in the through opening is connectedto the second multi-pin wire connector. Incident to the offset blindbore receiving the offset boss, the first multi-pin wire connector ismated with the second multi-pin wire connector for selectivelyelectrically connecting the control circuit to the sensing element withthe offset boss and offset bore ensuring proper alignment to the firstand second multi-pin wire connectors.

Other features and advantages will be apparent from a review of theentire specification, including the appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a process control instrument with arotatable and removable probe shown in a first angular orientation;

FIG. 2 is a view similar to FIG. 1, with the control head at a secondangular orientation;

FIG. 3 is a view similar to FIG. 1 with the control head removed;

FIG. 4 is a view similar to FIG. 1 with an additional cable for remotemounting of the control head;

FIG. 5 is an electrical schematic of the instruments of FIG. 1;

FIG. 6A is a side view of the connector assembly used with instrument ofFIG. 1;

FIG. 68 is a view similar to FIG. 6A showing first and second connectorsof the connector assembly of FIG. 6A in spaced apart relationship;

FIG. 7A is a side view of the first connector;

FIG. 7B is a perspective view of the first connector;

FIG. 7C is an end view of the first connector;

FIG. 8A is a side view of the second connector;

FIG. 8B is a perspective view of the second connector;

FIG. 8C is an end view of the second connector;

FIG. 9 is a sectional view of the connectors in spaced apartrelationship;

FIG. 10 is a sectional view of the connector assembly in a connectedstate; and

FIG. 11 is a sectional view showing the connector assembly in anintermediate position relative to those shown in FIGS. 9 and 10.

DETAILED DESCRIPTION

Referring to FIG. 1, a magnetostrictive level sensing instrument 20 isillustrated. As is conventional, the instrument 20 is operable to senselevel of a material, such as a fluid in a process vessel, and transmitan electrical signal indicative of the level to control instrumentation.

The instrument 20 includes a transmitter 22 and a probe 24 connected bya connector assembly 26. A magnetic 28 (usually part of a float) isreceivable on the probe 24. The transmitter 22 includes a controlhousing 30. The housing 30 comprises a dual compartment instrumenthousing as described in Mulrooney et al. U.S. Pat. No. 6,062,905, thespecification of which is incorporated by reference herein. The housing30 houses a sensing circuit, described below, for determining level andgenerating an electrical signal representing level for transmission toother control instruments, as is well known. A process adaptor 32 isprovided for mounting to a process vessel or the like and is operativelyconnected to the probe 24. The process adaptor 32 may take any knownform, such as a flange or threaded connector, as is conventional. Asdescribed herein, the connector assembly 26 is operatively disposedbetween the instrument housing 30 and the process adaptor 32.

The connector assembly 26 is rotatable, as illustrated by comparing theorientation of the control housing 30 in FIG. 2 relative to FIG. 1.Likewise, the control housing 30 is removable, as illustrated in FIG. 3,using the connector assembly 26. Finally, a cable 34, using a connectorassembly 26 at each end, as shown in FIG. 4, allows for remote mountingof the control housing 30 relative to the probe 24.

The magnet 28 comprises a conventional magnetic float, and isillustrated schematically. The magnet 28 is effectively captured on theprobe 24. As is known, the magnet, in the form of a float, floats atopthe material the level of which is being sensed and creates a magneticfield representative of the location of the top surface of the fluid orother material. As is apparent, the magnet 28 could be replaced byanother type of magnetic device for more generally sensing position ofthe magnet. Thus, the sensing instrument 20 could alternatively senseposition rather than level.

Referring to FIG. 5, the probe 24 has a conventional magnetostrictivewire 61 having a first end 62 and a second end 64. Both ends 62 and 64of the magnetostrictive wire 61 are connected to a drive circuit 66 of aprobe circuit 60. A pickup sensor crystal assembly 68 is operativelycoupled to the magnetostrictive wire 61, in any known manner. Forexample, the sensor crystal assembly 68 may sandwich themagnetostrictive wire 61 as shown in U.S. Pat. No. 7,466,124, owned bythe Assignee of the present application, the specification of which isincorporated by reference herein.

The sensor crystal assembly 68 is electrically connected to apreamplifier circuit 70 of the probe circuit 60. The probe circuit 60also includes a memory circuit 72. The memory circuit 72 is providedwith a write protect function.

The transmitter 22 includes a control circuit 74. The control circuit 74is connected via the connector assembly 26, as described below, to theprobe circuit 60. The control circuit 74 comprises a controller in theform of a programmed microcontroller 76. The microcontroller 76comprises a programmed processor and associated memory and I/O, such asa keypad and display (not shown), for operating in accordance with acontrol program to control operation of the instrument 20.

The connector assembly 26 connects a multi-conductor cable 78P from theprobe 24 to a multi-conductor cable 78T from the control circuit 74.These cables 78T and 78P include eight connector lines labelled A, B, C,D, E F, G and H.

The microcontroller 76 includes DRIVE+ and DRIVE− outputs connected viaconnector lines A and B to the drive circuit 66. A signal output fromthe preamp circuit 70 is connected via the connector line C to a signaloutput line of the microcontroller 76. The microcontroller 76 includesprobe memory interface ports connected via connector lines D and E tothe memory circuit 72. Connector lines F and G are provided for plusvoltage and ground, as illustrated. The swivel connector 26 illustratesa dashed line, representing a connector line H, used for a write protectinput of the memory circuit 72. This line H is only used during afactory calibration function, as described below, and does not connectto the microcontroller 76.

As is conventional, the microcontroller 76 controls the drive circuit 66to develop an electrical pulse on the magnetostrictive wire 61. Amagnetic field from the float 28 produces a torsional wave on themagnetostrictive wire 61 sensed by the sensor crystal assembly 68. Thiswave is used by the microcontroller 76 to determine position of thefloat 28, or more generally, the magnet, representing level whenimplemented as a level measuring instrument.

The illustrated embodiment comprises a process measurement instrument inthe form of a magnetostrictive instrument which can be used to senseposition of a magnet. In the illustrated embodiment, the magnet wouldfloat atop material level to indicate level. However, the connectorassembly described herein is not limited to a magnetostrictive typesensor or a level sensor. The connector assembly 26 could be used withother process measurement instruments including a sensing element forsensing a process variable and plural electrical conductors in a sensingelement for connection to a control circuit in a separate controlhousing. Examples of other type devices include capacitance, guided waveradar, ultrasonic and microwave radar, to name a few. This applicationis not directed to the specific control technology, but rather the useof a connector assembly for connecting an instrument housing to thesensing element.

Referring to FIGS. 6A and 6B, the connector assembly 26 comprises afirst connector 100 and a second connector 102. The first connector 100includes the probe cable 78P. The second connector 102 includes thetransmitter cable 78T. As is apparent, the connections could beopposite.

Referring to FIGS. 7A, 7B and 7C, the first connector 100 includes a onepiece metal cylindrical connector body 104. The connector body 104includes a coaxial through opening 106, see FIG. 9. The connector body104 is formed to include an upper end sleeve 108 separated by a flange110 from a threaded lower end 112. The threaded end 112 provides amechanical connection to the process adapter 32 or the control housing30, depending on the orientation of the connector assembly 26. Anannular groove 114 in the sleeve 108 just above the flange 110 receivesan O ring 116. The body 104 is narrowed above the sleeve 108 to define ashoulder 118 with an offset boss 120 extending upwardly therefrom. Adistal end of the boss 120 includes an annular rim 122. A blind bore 124is provided in the shoulder 118 in radial alignment with the throughopening 106 in the widest portion of the shoulder 118.

A first multi-pin wire connector 126 is receivable in the throughopening 106 and is flush mounted in the boss 120. In the illustratedembodiment, the wire connector 126 comprises a plastic body having eightpins for connection to the eight lines of the cable 78P, as will beapparent. A potting compound 128 fills the through opening 106, belowthe wire connector 126, see FIG. 9.

Referring to FIGS. 8A, 8B and 8C, the second connector 102 includes aone piece metal cylindrical connector housing 130 and a cylindricalswivel 132 rotatably mounted to the connector housing 130.

Referring also to FIG. 9, the connector housing 130 includes acylindrical body 134 having a coaxial through opening 136. The body 134narrows at a shoulder 138 to provide a neck 140. A first blind bore 142is provided at a connector end 144, opposite the neck 140, and definingan interior shoulder 146. The first blind bore 142 is coaxial with thethrough opening 136. A second blind bore 148 in the shoulder 146 isoffset from the first blind bore 142. The second blind bore 148 opens tothe through opening 136. The first blind bore is of a size and shape toreceive the connector body sleeve 108. The second blind bore 148 is of asize, shape and offset position to receive the offset boss 120,including the upper rim 122.

A second multi-pin wire connector 150 is partially receivable in thethrough opening 136 and extends into the offset blind bore 148 flushwith the shoulder 146. As such, the second multi-pin wire connector 150is coaxial with and aligned with the first multi-pin wire connector 126,as illustrated in FIG. 9. The second multi-pin wire connector 150comprises a plastic body with eight conductive terminals for connectingto the conductors of the transmitter cable 78T. The second multi-pinwire connector 150 is mateable with the first multi-pin wire connector126.

The swivel 132 comprises a collar 152 having an outer thread 154. Thecollar 152 provides a mechanical connection to the control housing 30 orthe process adapter 32, depending on the orientation of the connectorassembly 26. The collar 152 is receivable on the neck 140. A pair ofO-rings 156 and 158 are provided therebetween. A rectangular ring 159 ata top end 160 of the neck 140 retains the swivel 132 on the neck 140. Aroll pin 162 extending from the swivel 132 is receivable in an arcuategroove 164 in the housing shoulder 138 to limit rotation of the swivel132 relative to the connector housing 130. A locking set screw 166through the collar 152 selectively engages the neck 140 to lock theswivel in a desired position relative to the connector housing 130.

To prevent damage to the plastic wire connectors 126 and 150, theconnectors 100 and 102 must be aligned before the wire connectors 126and 150 begin to interlock during insertion. This is accomplished usingthe offset boss 120 in combination with the offset bore 148. Theconnectors 100 and 102 are illustrated disconnected in FIG. 9. As thefirst connector 100 is inserted into the second connector 102, as shownin FIG. 11, the sleeve 108 fits snugly within the first bore 142.However, before the wire connectors 126 and 150 mate, the firstconnector 100 must be rotated until the offset boss 120 is aligned withthe offset bore 148 to allow further insertion. With such alignment, thewire connectors 150 and 126 are properly aligned for full insertion andconnection, as illustrated in FIG. 10.

A pair of locking set screws 168 and 170 extend into the offset bore148, see FIGS. 8B and 8C, for selectively engaging the offset boss 120,just below the rim 122, to secure the first connector 100 to the secondconnector 102.

As with the first connector 100, a potting compound 72 fills the secondthrough opening 136 above the second wire connector 150. Thus, the wires78T and 78P are encapsulated with an approved flame retardant pottingcompound. Also, a cylindrical flame path FP1, see FIG. 10, is providedbetween the swivel 132 and the neck 140. Another cylindrical flame pathFP2 is provided between the first connector body 104 and a secondconnector housing 130.

As described herein, the transmitter 22 is selectively removable fromthe probe 24. This is done using the connector assembly 26 which enablesthe transmitter 22 to be removed from the probe 24, see FIG. 3, and tobe rotated relative to the probe 24, see FIG. 2. Alternatively, theconnector assembly 26 could be used with an elongate cable 34 to allowthe transmitter 22 to be remotely mounted relative to the probe 24, seeFIG. 4.

Particularly, the connector assembly 26 using the first connector 100and the second connector 102 enables the control housing 30 to beremoved from the process adaptor 32 and thus the probe 24 for servicingand the like. Also, the use of the swivel 132 allows the connectors 100and 102 to be rotatable relative to one another to provide a desiredorientation of the control housing 30. Moreover, a cable 34, see FIG. 4,including a third connector 100′, at one end, and similar to the firstconnector 100, and a fourth connector 102′ at an opposite end, andsimilar to the second connector 102, allows the control housing 30 to bemounted remotely relative to the process adaptor 32 with the samefittings as the connector assembly 26, on each end.

It will be appreciated by those skilled in the art that there are manypossible modifications to be made to the specific forms of the featuresand components of the disclosed embodiments while keeping within thespirit of the concepts disclosed herein. Accordingly, no limitations tothe specific forms of the embodiments disclosed herein should be readinto the claims unless expressly recited in the claims. Although a fewembodiments have been described in detail above, other modifications arepossible. Other embodiments may be within the scope of the followingclaims.

The invention claimed is:
 1. A process measurement instrumentcomprising: a process adapter for mounting to a process vessel andoperatively associated with a sensing element for sensing a processvariable and including plural electrical conductors; an instrumenthousing including a control circuit; and a connector assemblyoperatively disposed between the instrument housing and the processadapter for removably connecting the instrument housing to the processadapter, the connector assembly comprising a first connector including acylindrical connector body having an offset boss with a first multi-pinwire connector, and a second connector including a cylindrical connectorhousing, receiving the cylindrical connector body, having an offsetbore, receiving the offset boss, having a second multi-pin wireconnector, mateable with the first wire connector for selectivelyelectrically connecting the control circuit to the sensing element withthe offset boss and offset bore ensuring proper alignment of the firstand second multi-pin wire connectors.
 2. The process measurementinstrument of claim 1 wherein the cylindrical connector body comprises aone piece metal body threaded at one end, opposite the offset boss, forconnection to the process adapter or the instrument housing.
 3. Theprocess measurement instrument of claim 1 wherein the cylindricalconnector housing comprises a one piece metal housing.
 4. The processmeasurement instrument of claim 3 wherein the connector housing includesa neck at one end and a cylindrical swivel secured for rotation aroundthe neck, the swivel including an outer thread for connection to theprocess adapter or the instrument housing and enabling rotation of thecontrol housing relative to the process adapter.
 5. The processmeasurement instrument of claim 4 wherein the swivel includes a pinreceivable in an arcuate slot in the cylindrical connector housing tolimit rotation of the cylindrical swivel.
 6. The process measurementinstrument of claim 4 wherein the swivel includes a set screw engagingthe neck to selectively prevent rotation of the cylindrical swivel. 7.The process measurement instrument of claim 4 wherein the secondconnector is adapted to provide a cylindrical flame path between thecylindrical swivel and the neck and the cylindrical connector body andthe cylindrical connector housing are adapted to provide a secondcylindrical flame path to provide an explosion proof connector assembly.8. The process measurement instrument of claim 7 wherein the neckcomprises a through opening filled with a potting compound and thecylindrical connector body includes a through opening filled with apotting compound.
 9. The process measurement instrument of claim 1further comprising an elongate cable including a third connector,similar to the first connector, at one end, and a fourth connector,similar to the second connector, at an opposite end, for connecting thecable between the first and second connectors to remotely mount thecontrol housing relative to the process adapter.
 10. The processmeasurement instrument of claim 1 further comprising an o-ring disposedbetween the cylindrical connector body and the cylindrical connectorhousing.
 11. The process measurement instrument of claim 1 furthercomprising a lock screw receivable in an opening in the cylindricalconnector housing engaging the offset boss to secure the secondconnector to the first connector.
 12. A process measurement instrumentcomprising: a process adapter for mounting to a process vessel andoperatively associated with a sensing element for sensing a processvariable and including plural electrical conductors; an instrumenthousing including a control circuit; and a connector assemblyoperatively disposed between the instrument housing and the processadapter for removably connecting the instrument housing to the processadapter, the connector assembly comprising a first connector including acylindrical connector body with a coaxial through opening and having anoffset boss at one end with a first multi-pin wire connector in thethrough opening at the offset boss and a first electrical cable in thethrough opening connected to the first multi-pin wire connector, and asecond connector including a cylindrical connector housing with acoaxial through opening and a first blind bore at one end, receiving thecylindrical connector body, and an offset blind bore in the first blindbore, receiving the offset boss, a second multi-pin wire connector inthe offset blind bore and extending into the through opening and asecond electrical cable in the through opening connected to the secondmulti-pin wire connector, wherein incident to the offset blind borereceiving the offset boss the first multi-pin wire connector is matedwith the second wire multi-pin connector for selectively electricallyconnecting the control circuit to the sensing element with the offsetboss and offset bore ensuring proper alignment of the first and secondmulti-pin wire connectors.
 13. The process measurement instrument ofclaim 12 wherein the connector housing includes a neck at one end and acylindrical swivel secured for rotation around the neck, the swivelincluding an outer thread for connection to the process adapter or theinstrument housing and enabling rotation of the control housing relativeto the process adapter.
 14. The process measurement instrument of claim13 wherein the swivel includes a pin receivable in an arcuate slot inthe cylindrical connector housing to limit rotation of the cylindricalswivel.
 15. The process measurement instrument of claim 13 wherein theswivel includes a set screw engaging the neck to selectively preventrotation of the cylindrical swivel.
 16. The process measurementinstrument of claim 13 wherein the second connector is adapted toprovide a cylindrical flame path between the cylindrical swivel and theneck and the cylindrical connector body and the cylindrical connectorhousing are adapted to provide a second cylindrical flame path toprovide an explosion proof connector assembly.
 17. The processmeasurement instrument of claim 16 wherein the neck comprises a throughopening filled with a potting compound and the cylindrical connectorbody includes a through opening filled with a potting compound.
 18. Theprocess measurement instrument of claim 12 further comprising anelongate cable including a third connector, similar to the firstconnector, at one end, and a fourth connector, similar to the secondconnector, at an opposite end, for connecting the cable between thefirst and second connectors to remotely mount the control housingrelative to the process adapter.
 19. The process measurement instrumentof claim 12 further comprising an o-ring disposed between thecylindrical connector body and the cylindrical connector housing. 20.The process measurement instrument of claim 12 further comprising a lockscrew receivable in an opening in the cylindrical connector housingengaging the offset boss to secure the second connector to the firstconnector.